Topic
This occurs when you are experiencing an issue where Import/Export operations hang on certain existing wizards or some newly created ones, and the SEQ logs display the error "Sequence contains no matching element."

The user is missing the tenantId attribute in Aerobase.

Instructions 
Please verify the user (who attempted to export the wizard) from the Aerobase admin console under the "Attributes" tab. The respective user should have the "tenantId" key with the value "1."
Try logging in to Aerobase Admin Console using the URL below.
http://FQDN of application server/auth/admin/kryon/console/#realms/kryon

 
(Please use your server FQDN in the URL and the default credentials (Username: Authadmin, Password: Nintex123!). If you have changed the default credentials, please try using them.

Click on Users from the Manage Menu.

Click on View all users.

Select the username and click on Edit on the right. (For an example, please refer to the screenshot below for the test user.)

Select the username and click on Edit on the right. (For an example, please refer to the screenshot below for the test user.)

Select the Attributes tab as shown in the screenshot below.

Cross-check with Company Id in Nintex Admin. The values must be the same as tenantId.

Please try logging in to the Nintex Admin. Click on General on the left.

You can then re-sync the users from AD under "User Federation" using "Synchronize changed users" which will ensure the "TenantId" attribute is added to synced AD Users.

For non-AD users, you have to manually add the "tenantId" attribute.

Additional Information
If these steps do not resolve your issue, please send an email to Support@nintex.com, and let us know what troubleshooting you tried and the version you are using. We will be happy to assist right away.